[英]Objective-C dictionary argument is not an NSDictionary
我在这里有这行代码:
punchList = [[[NSMutableDictionary alloc]initWithDictionary:[[[areaData GetPunchListDataArray:communityDesc] objectForKey:@"Root"] objectForKey:@"KeyValue"]] autorelease];
但是当我运行它时,这会给我一个错误:
dictionary argument is not an NSDictionary
当我这样做:
punchList = [[[NSMutableDictionary alloc]initWithDictionary:[[areaData GetPunchListDataArray:communityDesc] objectForKey:@"Root"]] autorelease];
punchList = [punchList objectForKey:@"KeyValue"];
我没有得到任何错误,并且punchList被填充,为什么它不能正常工作我做的第一种方式。
如果将代码分解为具有单独变量的单独语句,则可能更清楚。 失败的例子可以分解为:
punchListDataArray = [areaData GetPunchListDataArray:communityDesc];
rootObject = [punchListDataArray objectForKey:@"Root"];
// This is not dictionary, so next line fails
possibleDictionary = [rootObject objectForKey:@"KeyValue"];
punchList = [[[NSMutableDictionary alloc]initWithDictionary:possibleDictionary] autorelease];
第二组陈述可以细分为:
punchListDataArray = [areaData GetPunchListDataArray:communityDesc];
rootObject = [punchListDataArray objectForKey:@"Root"];
// A different variable is being used to initialize
punchList = [[[NSMutableDictionary alloc]initWithDictionary:rootObject] autorelease];
punchList = [punchList objectForKey:@"KeyValue"];
仅仅因为行punchList = [punchList objectForKey:@"KeyValue"];
没有给你一个错误并不意味着结果是正确的。
尝试这个:
punchList = [[[NSMutableDictionary alloc]initWithDictionary:[[areaData GetPunchListDataArray:communityDesc] objectForKey:@"Root"]] autorelease];
punchList = [punchList objectForKey:@"KeyValue"];
NSLog(@"punchList is now a %@", [punchList class]);
id someValue = [punchList objectoForKey:@"SomeKey"];
运行该代码应该会崩溃,并在某些类上显示有关未知选择器objectForKey:
的消息。 并且控制台将显示日志消息,告诉您当时的punchList
实际是什么。
原因与您的第一个代码块失败的原因相同。 那是因为结果:
[[[areaData GetPunchListDataArray:communityDesc] objectForKey:@"Root"] objectForKey:@"KeyValue"]
不是NSDictionary
。
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